I used cylinder projection on this cylinder, but now there is a noticeable seam when i apply any texture, How can I make it seamless?
You can't make a non-seamless texture seamless, but you can find workarounds by using photoshop, or another program to make the texture seamless. I would either find a new texture, or use another program to make it seamless. There aren't too many other options, but finding a truly seamless texture should be pretty easy.